As far i can remember , there is no gtx 680 available in the market . .so better you should take gtx 670 gigabyte edition which is even better than gtx 680 reference model and priced 39k. And for future sli. . Tt toughpower 750w will be enough

750 will be sufficient..but toughpower is not a good PSU...you should go for toughpower grand or XT series as they are way better than toughpower...even smart is better than that one..anyway if you are going to sli/cf dont forget the importance of a good psu...a normal psu can handle single card system very well...but when theres multiple cards involved u shouldnt take risks with a normal psu